MEXICO CITY — Mexican business magnate Carlos Slim has overtaken Microsoft founder Bill Gates as the world's richest man, a Mexican financial journalist who has been tracking the mogul's wealth said Tuesday.

Slim controls Mexico's largest fixed-line telephone company and owns other businesses involved in everything from construction and music to restaurants and cigarettes. He was worth $67.8 billion at the end of the second quarter — equal to nearly 8 percent of Mexico's gross domestic product — said Eduardo Garcia, founder and director of sentidocomun.com.mx, a Mexico-based financial news Web site.

Forbes magazine reported on its Web site in April that Slim had moved past U.S. investor Warren Buffett to become the world's second-richest man, estimating Slim's fortune at just over $53 billion.

In its 2007 World Billionaire's List released in March, Forbes put Slim in third place behind Buffett and calculated Gates' wealth at $56 billion.

At that point, Garcia estimated that Slim had already overtaken Buffett, by about $1 billion as of the end of this year's first quarter.

Garcia attributes the second-quarter growth in Slim's wealth to a 26.5 percent increase in stock prices at one of the companies Slim controls, America Movil, the largest wireless service provider in Latin America.

Garcia also calculates that because of a 5.7 percent increase in Microsoft shares in the second quarter, Gates now has a fortune close to $59 billion, $8.8 billion less than Slim.

His latest calculations first appeared on the Sentido Común Web site Monday. Garcia, a former correspondent for Bloomberg financial news service, said he's been tracking Slim for about a year and a half.

"At some point I was looking at his holdings in the stock market and my numbers were much larger than what Forbes' were," he said.

In a statement issued Tuesday, Forbes did not comment on Garcia's calculations, but merely repeated its estimation of Gates' and Slim's wealth according to its most recent reports. The next valuation of Gates' worth will appear in the Forbes 400 list of the richest Americans in September, while a valuation of Slim's worth will be published in another World Billionaires list next March, the company said.

"As he has said many times himself, he is not in any competition," Ayub said. "He is dedicated to working in philanthropy and creating jobs in Latin America ... and the truth is he is not in a race to see who wins first or 10th or 15th place."